Classifications

• • A—HUMAN NECESSITIES
  • A62—LIFE-SAVING; FIRE-FIGHTING
  • A62D—CHEMICAL MEANS FOR EXTINGUISHING FIRES OR FOR COMBATING OR PROTECTING AGAINST HARMFUL CHEMICAL AGENTS; CHEMICAL MATERIALS FOR USE IN BREATHING APPARATUS
  • A62D1/00—Fire-extinguishing compositions; Use of chemical substances in extinguishing fires
  • A62D1/0064—Gels; Film-forming compositions
• • A—HUMAN NECESSITIES
  • A62—LIFE-SAVING; FIRE-FIGHTING
  • A62D—CHEMICAL MEANS FOR EXTINGUISHING FIRES OR FOR COMBATING OR PROTECTING AGAINST HARMFUL CHEMICAL AGENTS; CHEMICAL MATERIALS FOR USE IN BREATHING APPARATUS
  • A62D1/00—Fire-extinguishing compositions; Use of chemical substances in extinguishing fires
  • A62D1/0028—Liquid extinguishing substances
  • A62D1/0035—Aqueous solutions

Definitions

• This invention relates to chemical fire retardants and more particularly to concentrates adapted for dilution with water to produce long-term fire retardant solutions comprising such concentrates.
• Fire retardant mixtures adapted for release from fixed-wing aircraft are desirably of relatively high viscosity, for example, about 1000 to 2000 centipoise, so that the mixture resists atomizing or spreading out to form a thin, discontinuous layer as it falls from the aircraft.
• a mixture exhib­iting too high a viscosity is difficult to pump and may tend to form globules and so does not drop in fluid, continuous form to create an uninterrupted fire break.
• the viscosity of the mixture be maintained below about 3000 centi­poise, and more preferably below about 2000 centi­poise.
• fire retardant mixtures adapted for release from a heli­copter typically are of a relatively low viscosity, generally about 50 to 250 centipoise.
• Fire retardant mixtures employed in such fire control methods ordinarily comprise aqueous mixtures containing between about 5% and about 20% by weight, usually between about 10% and about 16% by weight, fire retardant.
• the retardant typically is a composition that produces phosphoric acid or sulfuric acid when heated.
• ammonium phosphate com­positions and ammonium sulfate compositions such as monoammonium orthophosphate, diammonium orthophosphate, monoammonium pyrophosphate, diammonium pyrophosphate, triammonium pyrophosphate, tetraammonium pyrophosphate, ammonium polyphosphate, substituted ammonium polyphos­phate, amide polyphosphate, melamine polyphosphate, ammonium-alkali metal mixed salts of orthophosphate, ammonium-alkali metal mixed salts of pyrophosphate, ammonium-alkali metal mixed salts of polyphosphate, ammonium-alkaline earth metal mixed salts of ortho­phosphate, ammonium-alkaline earth metal mixed salts of pyrophosphate, ammonium-alkaline earth metal mixed salts of polyphosphate, ammonium sulfate and blends thereof.
• liquid ammonium polyphosphates are also commonly used as fire retardants.
• Such liquid ammonium polyphosphates are often used commercially as fertilizers and may be aqueous mixtures of ammonium ortho, pyro, and polyphosphate and, optionally, also metaphosphate.
• Typical formulations of such liquid ammonium polyphosphates contain 10% by weight nitrogen and 34% by weight phosphorus, or 11% by weight nitrogen and 37% by weight phosphorus.
• fire suppressant mixtures rely solely on the water they contain to retard combustion
• phos­phate or sulfate containing fire retardant mixtures are useful for relatively long-term fire retardancy and include water primarily as a carrier for the fire retardant composition.
• long-term fire retardant mixtures continue to function even after the free water they contain evaporates.
• Long-term fire retardant mixtures are discussed in U.S. patent 4,145,296 (Fox et al.), U.S. patent 4,272,414 (Vandersall), U.S. patent 4,101,485 (Brooks et al.), U.S. patent 3,350,305 (Langguth et al.), U.S.
• patent 4,190,634 (Feiler), U.S. patent 3,558,486 (Morgenthaler), U.S. patent 3,364,149 (Morgenthaler), U.S. patent 3,342,749 (Handleman et al.), U.S. patent 3,338,829 (Langguth et al.), U.S. patent 3,309,324 (Langguth et al.), U.S. patent 3,293,189 (Morgenthaler), U.S. patent 3,275,566 (Langguth), U.S. patent 3,257,316 (Langguth et al.), U.S. patent 3,223,649 (Langguth), U.S. patent 3,024,100 (Langguth et al.), U.S. patent 3,024,099 (Martinson) and U.S. patent 2,526,083 (Nielson).
• aqueous long-term fire retardant mixtures When such aqueous long-term fire retardant mixtures are used to assist in gaining control of a fire, the retardant and the foliage coated by the retardant are heated. As an ammonium phosphate or ammonium sulfate retardant is heated, ammonia is released, leaving phosphoric or sulfuric acid on the cellulose of the foliage, whereupon a reaction is understood to take place and, as a by-product, water is given off as fire suppressing steam.
• the com­positions which act as retardants are salts or other compounds that release phosphoric acid or sulfuric acid below the ignition temperature of cellulose.
• Aqueous fire retardant mixtures are frequently prepared by mixing a solid powder form fire retardant mixture with water. Such mixtures may also be prepared by diluting liquid ammonium phosphate with water.
• fire control mixtures further con­tain a gum thickener to modify the viscosity of the mixture.
• Low viscosity mixtures contain a relatively lower proportion of thickener than do high viscosity mixtures.
• Some typical gum thickeners are discussed in U.S. patent 3,634,234 (Morgenthaler), in U.S. patent 4,447,336 (Vandersall) and in U.S. patent 4,447,337 (Adl et al.).
• the mixture may contain corrosion inhibitors and flow conditioners.
• Aqueous fire retardant solutions are frequently prepared by mixing a solid powder form fire retardant composition with water.
• Typical flow conditioners which are added to the powder form of the fire control mixture to keep the mixture free-flowing, are tricalcium phosphate, magnesium carbonate, talc, sodium silicate and finely divided, colloidal silica.
• the aqueous fire control mixture may also contain a colorant.
• the colorant may be a pigment such as iron oxide, which produces a red color, titanium dioxide pigment, which produces a white color, or an ultra-violet sensitive dye dispersed in biodegradable plastic.
• the mixture as used in fire control, comprises a relatively dilute solution or suspension of active ingredients and other auxiliary components in water, it is more economical to ship and store the fire control mixture in a relatively concentrated, lighter and less voluminous dry form, and to dilute the dry or liquid concentrate form on site or as needed. Further, because of the emergency nature of fire fighting, the frequent lack of manpower and the desirability of mini­mizing potential mechanical failure, it is frequently preferred to have a concentrated liquid retardant com­position which can be merely diluted before use rather than a dry powder composition which must be mixed.
• a fire retard­ant concentrate that reduces shipping costs by avoiding transporting large quantities of water which can be obtained on site; the provision of such concentrate that is as easily handled as a water-like liquid; the provision of such concentrate that can be diluted accurately with simple equipment to a high viscosity, elastic gum thickened mixture of end use concentration; the provision of a method for preparing such concen­trate; and the provision of a method for preparing a fire control retardant from such concentrate.
• the present invention is directed to a novel aqueous concentrate adapted to be diluted with water and used in fire control.
• the con­centrate exhibits a viscosity of less than about 3000 centipoise and contains between about 0.75% and about 6% by weight thickening agent and at least about 24% by weight solids derived from a fire retardant selected from the group consisting of diammonium phosphate, diammonium sulfate, a blend of diammonium phosphate and diammonium sulfate, a blend of monoammonium phosphate and diammonium phosphate having a nitrogen to phos­phorus ratio of at least about 1.25, a blend of monoam­monium phosphate, a diammonium sulfate and diammonium phosphate having a nitrogen to phosphorus ratio of at least about 1.25, and a blend of such fire retardant with polyammonium phosphate.
• the present invention is also directed to a novel aqueous concentrate that is adapted to be diluted with water to produce an aqueous fire retardant mixture exhibiting a viscosity of between about 1000 centipoise and about 3000 centipoise and containing between about 5% and about 20% by weight fire retardant and between about 0.2% and about 3% by weight thickening agent.
• the characteristics of the fire retardant component are such that (a) the fire retardant releases phosphoric acid or sulfuric acid or both at a temperature below the ignition temperature of cellulose; and (b) mixing of one part by weight of the fire retardant component with between about 6 and about 20 parts by weight water and between about 0.02 and about 0.2 parts by weight thickening agent produces a mixture having a viscosity of between about 1000 and about 3000 centipoise; but (c) mixing of one part by weight of the same fire retardant component with less than about 4 parts by weight water and between about 0.02 and about 0.2 parts by weight thickening agent produces a mixture having a viscosity less than about 1000 centipoise.
• the present invention is further directed to a novel aqueous concentrate that contains such fire retardant and is adapted to be diluted with water to produce a fire retardant mixture exhibiting a viscosity of between about 50 centipoise and about 250 centipoise and containing between about 5% and about 20% by weight fire retardant.
• the present invention is also directed to a novel method for preparing an aqueous concentrate that is adapted to be diluted with water and used in fire control.
• the method comprises mixing a fire retardant composition with water to produce a concentrate exhib­iting a viscosity of less than about 2000 centipoise and having a concentration of solids derived from the fire retardant composition of at least about 30% by weight of total concentrate, 40 parts by weight total fire retardant composition containing between about 1 and about 3 parts by weight of a thickening agent and between about 34 and about 38 parts by weight of a fire retardant.
• the characteristics of the fire retardant component are such that (a) the fire retardant releases phosphoric acid or sulfuric acid or both at a tempera­ture below the ignition temperature of cellulose; and (b) mixing of one part by weight of the fire retardant component with between about 6 and about 20 parts by weight water and between about 0.02 and about 0.2 parts by weight thickening agent produces a mixture having a viscosity of between about 1000 and about 3000 centi­poise; but (c) mixing of one part by weight of the same fire retardant with less than about 4 parts by weight water and between about 0.02 and about 0.2 parts by weight thickening agent produces a mixture having a viscosity less than about 1000 centipoise.
• the mixing is carried out in a manner such that the concentration of fire retardant composition in the aqueous phase remains above about 30% by weight during the entire mixing process.
• the present invention is also directed to a novel method for preparing an aqueous concentrate that is adapted to be diluted with water and used in fire control, wherein the method comprises mixing a solid particulate fire retardant composition with water to produce a concentrate exhibiting a viscosity of less than about 2000 centipoise and a concentration of solids derived from the fire retardant composition of at least about 30% by weight of total concentrate, 40 parts by weight total fire retardant composition con­taining between about 1 and about 3 parts by weight of a thickening agent and between about 34 and about 38 parts by weight of a fire retardant.
• the fire retard­ant is selected from the group consisting of diammonium phosphate, diammonium sulfate, a blend of diammonium phosphate and diammonium sulfate, a blend of monoammon­ium phosphate and diammonium phosphate having a nitro­gen to phosphorus ratio of at least about 1.25, a blend of monoamonium phosphate, diammonium sulfate and diam­monium phosphate having a nitrogen to phosphorus ratio of at least about 1.25, and a blend of such fire retardant with polyammonium phosphate.
• mixing being carried out in a manner such that the concentration of fire retardant composition in the aqueous phase remains about about 30% by weight during the entire mixing process.
• the present invention is also directed to a novel multiple step method for preparing an aqueous concentrate that is adapted to be diluted with water and used in fire control.
• a solid particulate fire retardant is mixed with water to pro­duce a retardant solution having a concentration of solids derived from the fire retardant of at least about 24% by weight of solution.
• the characteristics of the fire retardant component are such that (a) the fire retardant releases phosphoric acid or sulfuric acid or both at a temperature below the ignition temperature of cellulose; and (b) mixing of one part by weight of the fire retardant component with between about 6 and about 20 parts by weight water and between about 0.02 and about 0.2 parts by weight thickening agent produces a mixture having a viscosity of between about 1000 and about 3000 centipoise; but (c) mixing of one part by weight of the fire retardant component with less than about 4 parts by weight water and between about 0.02 and about 0.2 parts by weight thickening agent produces a mixture having a viscosity less than about 1000 centipoise.
• composition com­prising a thickening agent is mixed with the solution to produce a concentrate comprising at between about 0.75% and about 6% by weight thickening agent and exhibiting a viscosity of less than about 1000 centi­poise.
• the present invention is further drawn to such method wherein the fire retardant is selected from the group consisting of diammonium phosphate, diammon­ium sulfate, a blend of diammonium phosphate and diam­monium sulfate, a blend of monoammonium phosphate and diammonium phosphate having a nitrogen to phosphorus ratio of at least about 1.25, a blend of monoammonium phosphate, diammonium sulfate and diammonium phosphate having a nitrogen to phosphorus ratio of at least about 1.25, and a blend of such fire retardant with polyam­monium phosphate.
• the fire retardant is selected from the group consisting of diammonium phosphate, diammon­ium sulfate, a blend of diammonium phosphate and diam­monium sulfate, a blend of monoammonium phosphate and diammonium phosphate having a nitrogen to phosphorus ratio of at least about 1.25
• the present invention is also directed to methods of preparing fire retardant mixtures from such concentrates and to methods of controlling fires with such mixtures.
• an aqueous fire retardant concentrate can be prepared, having a moderate viscos­ity despite the presence of a thickener, by maintaining the concentration of fire retardant in the concentrate at a high level. More particularly, it has been found that, by maintaining the concentration of certain fire retardants above about 24% by weight, the viscosity of the concentrate is controlled at less than about 2000 cps, even in the presence of 6% and possibly as much as 50% by weight of a thickening agent.
• the viscosity of a mixture would be expected to increase with increasing concentration of thickener or other high-viscosity components. And, as expected, it has been found that increasing the concentration of fire retardant in an aqueous fire control mixture from about 10% to 20% by weight (while maintaining a constant thickener to retardant con­centration ratio), increases the viscosity of the mixture.
• the concentrate of this invention which has a fire retardant concentra­tion of at least about 24% by weight and a thickener concentration of between about 0.75% and 6% by weight, not only has a viscosity that is not appreciably higher than that of the diluted mixture ultimately used in fire control, (5% to 10% by weight fire retardant and at most about 0.3% by weight thickener) but typically the concentrate has a much lower viscosity than the diluted mixture. Yet this phenomenon has been found not to be determined by the pH of the concentrate, and has been observed only for certain fire retardants.
• the viscosity of the concentrate is very high.
• the retardant in a concentrate of the same pH is diammonium sulphate, the viscosity of the concentrate is relatively low. It has been found that the concentrate of this invention has a viscosity far below 2000 centipoise, typically below about 350 centipoise and often below about 50 centipoise.
• the concentrate of this invention avoids the pumping and handling problems that are encountered with mixtures of viscosities above about 2000 centipoise.
• the aqueous concentrate tends to disperse into mixture during dilution more readily than does powder. Accordingly, the con­centrates of this invention require less meticulous metering of water than is required for ordinary powder concentrates.
• the concentrate since the concentrate includes thickener and, optionally, other additives, the only ingredients necessary on-site to produce a fire control retardant ready for application are the concentrate and water.
• fire retardants produce mixtures exhibiting viscosities of between about 1000 and about 2000 centipoise when one part by weight of the fire retardant is mixed with between about 0.055 and about 0.2 parts by weight thickening agent and between about 6 and about 20 parts by weight water. Yet, these same retardants produce mixtures exhibiting viscosities below 1000 centipoise when one part by weight fire retardant is mixed with the same amount of thickening agent, but less than about 4 parts by weight water. This is a significant advantage in preparing and handl­ing concentrates of high viscosity fire control retard­ants adapted for application by fixed-wing aircraft.
• the fire retardant produces a mixture exhibiting a viscosity between about 50 and about 250 centipoise when one part by weight of the fire retardant is mixed with between about 0.02 and about 0.075 parts by weight thickening agent and between about 6 and about 20 parts by weight water.
• the fire retardant produces a mixture exhibit­ing a viscosity below 50 centipoise when one part by weight fire retardant is mixed with the same amount of thickening agent, but less than about 4 parts by weight water.
• this is a significant advantage in preparing and handling concentrates of high viscosity fire control retardants adapted for application by helicopter.
• the fire retardants of the concentrates and fire control retardants of the invention are compounds or a mixture of compounds that degrade or decompose at temperatures below the ignition temperature of the fuels to be protected (e.g., cellulose), thereby releasing a mineral acid, such as phosphoric acid or sulfuric acid.
• fire retardants typi­cally used in fire retardant mixtures and which might be used in the concentrate of this invention are mono­ammonium orthophosphate, diammonium orthophosphate, monoammonium pyrophosphate, diammonium pyrophosphate, triammonium pyrophosphate, tetraammonium pyrophosphate, ammonium polyphosphate, substituted ammonium polyphos­phate, amide polyphosphate, melamine polyphosphate, ammonium-alkali metal mixed salts of orthophosphate, ammonium-alkali metal mixed salts of pyrophosphate, ammonium-alkali metal mixed salts of polyphosphate, ammonium-alkaline earth metal mixed salts of ortho­phosphate, ammonium-alkaline earth metal mixed salts of pyrophosphate, ammonium-alkaline earth metal mixed salts of polyphosphate, ammonium sulfate, liquid ammon­ium polyphosphates and blends thereof.
• liquid ammonium polyphosphates are generally too dilute in their commercial forms for application as fire retard­ants, other retardants, such as those noted above, may be mixed with liquid ammonium polyphosphate until a minimum acceptable concentration is obtained.
• Ammonium polyphospohate is often called polyammonium phosphate, and commonly contains other ammonium phosphate such as pyroand metaphophates, and the alkali metal equivalents thereof, as well as a blend of phosphate polymers.
• Such polyammonium phosphates are often referred to as 10-34-0, 11-37-0, 12-40-0, 13-42-0 or the like, where the first number indicates the percentage of nitrogen in the blend, the middle number indicates the percent­age phosphate in the blend and the last number indi­cates the percentage potash in the blend.
• DAP diammon­ium phosphate
• DAS diammonium sulfate
• MAP monoammonium phosphate
• Typical commercial blends comprise MAP and DAP in ratios ranging from about 9:1 to about 1:9.
• One particular blend contains about 30 parts by weight DAS and about 9 parts by weight MAP per 1 part by weight DAP. It has been found, however, that for a MAP containing concentrate to have a viscosity below about 2000 centipoise, the concentrate should contain at least 0.3 mole DAP per mole of MAP.
• the MAP:DAP ratio tends to affect the pH of concentrates of this invention, with a concentrate of high MAP:DAP ratio having a pH of about 5.5 to 6, and a low MAP:DAP ratio concentrate having a pH near 8.
• the fire retardants are commonly available in solid, particulate form but may also be obtained in a concentrated thickener-free aqueous solution requiring dilution with water and addition of thickener and other additives before application to wildland for fire con­trol.
• the concentrated aqueous solution of commerce typically contains 34% to 42% by weight P2O5 (15% to 18% by weight phosphorus) in the form of ammonium ortho, pyro and polyphosphates, water and various impurities, but no thickening agent or other intended additive.
• the retardant may first be mixed with water.
• a solid particulate premix comprising thickener and other additives, is mixed with the water with which the retardant was mixed.
• the solid, particulate fire retardant is added independently, and before the thickener. It is also possible to simul­taneously add the thickener and retardant to water under agitation. Therefore, the solid, particulate form of fire retardant may be combined with the thick­ener and other additives to form a dry solid, particu­late fire retardant composition for mixing with water.
• Such dry solid, particulate fire retardant composition may contain between about 85% and 95% by weight fire retardant, between about 2.5% and about 7.5% by weight gum thickener, between about 1% and about 5% by weight corrosion inhibitor, up to about 4% by weight color pigment and other functional components as desired.
• the thickening agent of the composition of this invention may be any of a number of thickeners, including standard gum thickeners such as galactomannan guar gum compositions.
• the thickening agent is employed to maintain the viscosity of the diluted fire retardant solution, for example, at between about 1000 centipoise and about 2000 centipoise for aerial bom­bardment from fixed-wing aircraft, or between about 50 centipoise and about 250 centipoise for aerial bombard­ment from helicopter.
• the thickener should make up between about 0.75% and about 6% by weight of the con­centrate.
• the thickener concentration in the concentrate can be even higher, but the specific con­centration depends on the viscosity desired in the diluted mixture.
• the thickener concentration in the concentrate for fixed-wing aircraft applications should be between about 1.9% and about 6% by weight of the concentrate to produce an expanded mixture upon dilution exhibiting a viscosity of between about 1000 cps and about 2000 cps, and comprising about 0.8% or 0.9% by weight thickener.
• the thickener concentration in the concentrate for helicopter applications should be between about 0.25% and about 2% by weight of the concentrate to produce an expanded mixture upon dilution exhibiting a viscosity of between about 50 cps and about 250 cps, and preferably is between about 0.28% and about 0.36% by weight thickener.
• composition of this invention may also contain a pigment such as iron oxide, which produces a red color, titanium dioxide pigment, which produces a white color, or a fugitive pigment which fades upon exposure to the elements.
• a pigment such as iron oxide, which produces a red color, titanium dioxide pigment, which produces a white color, or a fugitive pigment which fades upon exposure to the elements.
• These colors aid a fire­fighting pilot by enabling the pilot to see where fire retardant solutions have already been dropped.
• the concentrate would contain as much color pigment as would be required for visibility upon dilution. Thus, the amount of pigment depends on the degree of dilution contemplated.
• flow conditioners such as tricalcium phosphate, magnesium carbonate, talc, sodium silicate and finely divided colloidal silica, added to keep the powder form of fire retardant composition free-flowing; and defoaming and antifoaming agents, such as polyalkylene derivatives of propylene glycol.
• defoaming and antifoaming agents such as polyalkylene derivatives of propylene glycol.
• ferrous ions are believed sometimes to result from certain methods of production of the fire retardant, but also result from corrosion by certain fire retardant concentrates or mixtures of iron or steel holding tanks.
• the ferrous ions are believed to impair the stability of the concentrates and fire control retardants made therefrom, when the concentrate or related mixtures are to be stored in iron or steel tanks, it is preferred that small amounts of corrosion inhibitors (usually less than about 0.1% by weight), such as sodium silicofluoride, dimercaptothiadiazole and/or sodium thiosulfate, be added to the concentrates of this invention to minimize the iron introduced into the concentrate from corrosion.
• corrosion inhibitors usually less than about 0.1% by weight
• the water used in formation of the aqueous concentrate and in dilution of the concentrate may be tap water or water from other convenient water sources. Due to the potentially long periods of storage and the danger of bacteria growth supported by the gum thickener (which typically is a polysac­charide), it may be desirable that the water be sub­stantially bacteria-free. Accordingly, it may be desirable to add a bacteriocide, such as sodium silico­fluoride in a proportion of about 0.90% by weight sod­ium silicofluoride in the concentrate. The bacterio­cide may be added to the water either before, after or simultaneously with incorporation of the fire retardant and thickener. However, the aqueous mixtures of this invention tend to have high ionic strength, so it is believed that use of bacteria-free water or a bacterio­cide is not always necessary.
• the aqueous concentrate of this inven­tion contains at least about 24% and as much as about 75% by weight fire retardant, between about 0.75% and about 6% by weight thickening agent, minor amounts of other additives as discussed above, and exhibits a viscosity below about 2000 centipoise.
• a fire retardant solution for helicopter delivery is prepared by diluting a concentrate of appropriate composition with enough water to lower the concentration of the fire retardant to between about 5% and 20% by weight of the mixture, the mixture obtained exhibits a viscosity between about 50 centipoise and about 250 centipoise.
• a fire control retardant for fixed-wing aircraft delivery is prepared in a comparable manner, the mixture obtained exhibits a viscosity between about 1000 centipoise and about 2000 centipoise.
• the aqueous concentrate of this invention should be prepared by mixing fire retardant with water in a manner such that the fire retardant concentration in the mixture does not fall below about 24% by weight during incorporation of the thickening agent into the concentrate.
• the thickener should not be added before the retardant, since it has been found that retardant-free mixtures which contain even 1.5% by weight thickener exhibit unmanageably high viscosity.
• the low viscosity concentrates of this invention cannot be formed from the mixture even by adding large amounts of fire retardant.
• Such premixture would be a thick paste or solid if the pre­mixture contained a high enough thickener concentrate so that a proper resulting thickener concentration is reached upon dilution of the premix with retardant/­water mixture.
• the viscosity does not decrease to a satisfactory level upon addition to the fire retard­ant/water mixture.
• the fire retardant is first mixed with water to a concentration of a least 24%, after which the thickener is added to the fire retardant and water mixture.
• thickener and fire retardant may be mixed with water simultaneously and quickly and with agitation. Due to the higher dissolution rate of the retardant, it tends to dissolve in water more quickly than the thickener and it has been found that the overly high viscosity is avoided.
• the water may be added to a fire retardant composition comprising fire retardant and thickener, or such fire retardant com­position and water may be introduced simultaneously to a mixing chamber.
• a fire retardant composition comprising fire retardant and thickener, or such fire retardant com­position and water may be introduced simultaneously to a mixing chamber.
• slow addition of fire retardant composition to a large volume of water results, at some point during the mixing process, in a retardant composition concentration which exhibits an inconveniently high viscosity.
• the con­centrate may be prepared by mixing dry solid, particu­late fire retardant with water until the desired con­centration is reached, and then mixing the resulting retardant solution with a "premix" comprising thickener and other additives.
• a very highly con­centrated thickener-free aqueous retardant solution may be mixed with premix. If the resultant fire retardant concentration is higher than desired in the concen­trate, water may be added to achieve the proper retardant concentration for the concentrate of this invention.
• the concentrate of this invention can be stored in a tank near the site of potential wildland fires.
• the tank may be equipped either with a small pump to recirculate the concentrate or with a slow agitator to maintain the homogeneity of the concen­trate.
• Another method of maintaining the homogeneity might be to thicken the concentrate by adding a rela­tively small amount of a second thickener that would be more effective in the concentrate than the original thickener.
• the concentrate may be diluted well in advance of any fire to form the expanded fire control retardant.
• the mixture may then be stored in its expanded form.
• the fire retardant solution as employed in control of fire ordinarily contains between about 5% and about 20% by weight fire retardant and between about 0.2% and about 3.0% by weight thickener.
• the concentrate may be diluted in a holding tank.
• the concentrate and water may be introduced from separate feed lines into a common conduit wherein mixing takes place.
• the resultant fire retardant solution may be discharged directly from the mixing conduit into a delivery tank inside the delivery vehicle.
• DAP diammonium phosphate
• the viscosity of the solution measured 10 minutes after mixing of this con­centrate was measured with a Brookfield viscometer operating at 60 rpm and was found to be about 22 cps. A portion of the concentrate was then diluted with tap water to form a mixture comprising 16.1% by weight solids derived from the composition. The 10 minute viscosity of this mixture was found to be about 112 cps. The viscosity of the remaining concentrate remained 22 cps when measured at a later time.
• mixture j Three more mixtures were prepared as above, but instead of the high viscosity, high proportion DAP fire retardant composition, the following compositions were used.
• the composition comprised the following:
• composition comprised the following:
• composition comprised the following:
• Example 2 The mixtures of Example 2 were stored in tightly capped jars for about forty hours. Then a sample of each mixture was diluted with some agitation to a 12% solution as might be used in fire control. The viscosity of each diluted mixture was measured by the procedure of Example 1 with the following results (the 40 hr. visc. is the viscosity of the mixture before dilution to a 12% solution, but after sitting for forty hours; the 10 min. visc. is the viscosity ten minutes after dilution; and the 2 hr. visc. is the viscosity two hours after dilution): Sample i was rerun with the dilution performed without agitation.
• the concentrate was stirred into water and the resulting mixture sat for ten minutes.
• the viscos­ity ten minutes after dilution was found to be 1847 cps, and the viscosity two hours after dilution was found to be 2040 cps.
• Sample i was again rerun with the dilution performed with agitation.
• the viscosity ten minutes after dilution was found to be 1718 cps, and the viscosity two hours after dilution was found to be 1833 cps.
• Concentrate A was prepared by dissolving dry powder MAP (1047.5 lbs.) and dry powder DAP (698.5 lbs.) in water (2660 lbs.) and then adding a blended dry premix (254.0 lbs.) consisting of by weight of total premix: 57.2% colloid thickener (a polysaccharide guar gum) 16.4% tricalcium phosphate 2.3% mercaptobenzothiazole 1.5% sodium molybdate 5.7% dimercaptothiadiazole 3.7% sodium silicofluoride 12.1% fugitive color 1% polyalkylene derivatives of propylene glycol Concentrate B was prepared in the same manner, except that less water (2283 lbs. as opposed to 2660 lbs.) was used.
• Concentrate C was prepared by dissolving dry powder MAP (1069.6 lbs.) and dry powder DAP (713.5 lbs.) in water (2760 lbs.) and then adding a blended dry premix (217.0 lbs.) consisting of by weight: 68.5% colloid thickener 2.8% mercaptobenzothiazole 1.8% sodium molybdate 6.8% dimercaptothiadiazole 4.4% sodium silicofluoride 14.5% fugitive color 1.4% polyalkylene derivatives of propylene glycol Concentrate D was prepared in the same manner, except that less water (2375 lbs. as opposed to 2760 lbs.) was used.
• the concentrates were stirred or shaken to increase the homogeneity, and an aliquot sample was withdrawn from each concentrate. Under agitation, each sample was then diluted with water in the following ratios in pounds of concentrate per pound of water: for A, 3.00; for B, 3.35; for C, 2.99; and for D, 3.34.
• the composition of the concentrates and the diluted mixtures are shown in the following tables and compared to the corresponding exemplary requirements set forth by the government of Italy:
• Concentrated thickener-free, high DAP concen­tration fire retardant solution was obtained and analyzed.
• the solution was of low quality grade (i.e., high concentration of impurities), cloudy and yellow­ish, had a pH of 6.95, a phosphate (in the form of P2O5) concentration of 19.71% by weight and a ferrous ion content of 0.070% by weight.
• Hydroxypropyl guar thickener (6 gm.) was added to a sample (200 gm.) of the solution to produce a suspension exhibiting a viscosity of 40 centipoise.
• a second sample (97.3 gm.) of the low quality grade thickener-free solution was mixed with water (247.6 gm.) and a premix comprising gum thickener (3.165 gm.), sodium silicofluoride (0.95 gm.), sodium thiosulfate (0.316 gm.), mercaptobenzothiazole (0.127 gm.), fugitive color (0.675 gm.), tricalcium phosphate (0.844 gm.) and antifoaming agent (0.063 gm.) to form Mixture 1.
• Another sample was neutralized by adding aqueous ammonia (about 1.4% by weight) to increase the pH to 7.9.
• the neutralized sample (100 gm.) was mixed with water (244.9 gm.) and the same amount of premix as used to make Mixture 1.
• the resulting mixture was labeled Mixture 2.
• the viscosities of the two mixtures were measured with Brookfield Viscometer Model LVF at 60 rpm and spindle number 4 at various times after dilution and the results were as follows:
• Sample A Two more samples, A and B, of the thick­ener-free fire retardant solution were obtained.
• the pH of one sample, Sample A was increased to 8.0 by bubbling anhydrous NH3 into the liquid with agita­tion.
• Each sample was mixed with a premix to form a sample containing the fire retardant solution (94.84% by weight), gum thickener (3.09% by weight), sodium silicofluoride (0.93% by weight), sodium thiosulfate (0.31% by weight), mercaptobenzothiazole (0.12% by weight), fugitive color (0.66% by weight) and antifoam (0.05% by weight).
• Sample A was separated into Samples A-1, A-2 and A-3.
• premix (24.3 g,.), containing thickener (15.00 gm.), fugitive color (2.70 gm.), mercaptobenzothiazole (0.60 gm.), sodium silicofluoride (4.50 gm.) and sodium thiosulfate (1.50 gm.) plus other additives as shown in the tables below, and polyalkylene derivative of propylene glycol were added to each aliquot. After mixing, the 10 minute viscosity of each aliquot was measured. Then, the aliquots were homogenized by agitation and a por­tion (120 gm.) of each aliquot was removed and stored.
• Example 1 Two thickener-free, low quality liquid con­centrate samples were obtained. One of the samples was filtered in an effort to eliminate impurities. Analy­sis of the unfiltered sample (Sample 1) indicated that it contained by weight 23.59% P2O5, 8.77% NH3, 2.47% SO4 and 100 ppm Fe+2, had a pH of 6.50, had a specific gravity of 1.292 kilograms per liter and had a nitrogen to phosphorus molar ratio of 1.55.
• Example 2 Analysis of the filtered sample (Sample 2) indicated that it contained by weight 23.39% P2O5, 8.42% NH3, 1.23% SO4 and 89 ppm Fe+2, had a pH of 6.38, had a speci­fic gravity of 1.266 kilograms per liter and had a nitrogen to phosphorus molar ratio of 1.50. The analyses, therefore, indicated that the samples were about 40% by weight mono and diammonium phosphate in 1:1 molar ratio. The unfiltered sample was greenish brown, the filtered sample was yellow and both samples contained considerable quantities of fine, nearly colloidal insolubles. It appeared that the samples were prepared from wet-acid grade phosphoric acid.
• a third sample (Sample 3) was prepared by dissolving dry solid, particulate DAP (1 kg.) in dis­tilled water (1.34 liters).
• the third sample contained 23.13% by weight P2O5 and had a pH of 6.80.

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